Precipitation within EUREC4A: a multi-sensor ship-based approach to tackle warm rain processes

Trade wind cumulus clouds play a vital role in the Earth's radiation budget and produce up to 20% of the total precipitation in the tropics. However, we still don't know how they will respond to global warming. Precipitation from trade wind cumuli can alter cloud macroscopic properties and the boundary layer structure and dynamics.

Precipitation development in models is very uncertain, being dependent on simulation setup and microphysics. In particular, the autoconversion scheme dramatically affects precipitation flux, cloud structure, and organization. Currently, no evaluations of the different autoconversion schemes with observations reduced the uncertainties in rain processes. Precipitation can impact convection organization and circulation intensity with massive effects on climate sensitivity and its evaporation determines the intensity of cold pools and influences the cloud field organization. It is hence key to quantify evaporation rates and their spatiotemporal variability. Parametrizations of evaporation below cloud base are available but strongly depend on the drop size distribution of raindrops. Also, in the observations, evaporation rates are hard to observe directly.

Here, we would like to present the potential given by the observations collected on the Maria S. Merian ship during the EUREC4A campaign to estimate evaporation rates and provide advanced multi-sensor observations of rain onset and development. The synergy of multiple in-situ and remote-sensing from the ship as well as aircraft observations available will allow to constrain the autoconversion scheme in LES models and reduce the uncertainties connected to rain processes. Moreover, quantification of evaporation rates will clarify the role of precipitation in moisturizing the boundary layer in trade wind regions.